Thermostatic bimetal and high expanding alloy

ABSTRACT

A HIGH EXPANDING COMPONENT FOR A THERMOSTATIC BIMETAL IN THE FORM OF AN ALLOY HAVING AS MAJOR CONSTITUENTS, NICKEL, CHROMIUM, IRON AND MANGANESE. A BIMETAL UTILIZING THIS COMPONENT TOGETHER WITH A CONVENTIONAL LOW EXPANDING COMPONENT SUCH AS INVAR CAN BE USED WITHIN A TEMPERATURE RANGE OF -196*C. TO 250*C. WITHOUT ANY LOSS OF STRENGTH OR ELASTICITY SINCE, UNLIKE CONVENTIONAL BIMETALS, NEITHER OF THE TWO COMPONENTS USED IN MY BIMETAL UNDERGOES ANY TYPE OF PHASE INFORMATION.

United States Patent US. Cl. 29--195.5 2 Claims ABSTRACT OF THE DISCLOSURE A high expanding component for a thermostatic bimetal in the form of an alloy having as major constituents, nickel, chromium, iron and manganese. A bimetal utilizing this component together with a conventional low expanding component such as Invar can be used within a temperature range of 196 C. to 250 C. without any loss of strength or elasticity since, unlike conventional bimetals, neither of the two components used in my bimetal undergoes any type of phase information.

BACKGROUND OF THE INVENTION Bimetals using a high expanding component of the chromium-nickel-iron type (typically an alloy containing 22% nickel, 3% chromium, balance iron) and a low expanding component of the nickel-iron type (typically 35.5%-50% nickel, balance iron) cannot be used below -100 F. (73 C.) without detrimental effects, since the high expanding component is normally in the austenite phase, but undergoes an incomplete martensitic transformation at subzero temperatures whereby a two phase structure (austenite plus martensite) is produced. This transformation is accompanied by a permanent discrete volume increase so that this component is not dimensionally stable at low temperatures. Upon subsequent heating, the thermal expansion of this component is decreased. As a result of this decrease, the flexivity (the amount of bend of the bimetal when heated) of a bimetal having a component with a two phase structure is substantially reduced over the flexivity which would be obtained if the component remained single phase.

SUMMARY OF THE INVENTION I have developed an alloy containing the following major constituents as expressed in percent by weight:

Percent Nickel 20.2-21.5 Chromium 3.2-5.0 Manganese 0.5-2.2

Iron, balance.

The following minor constituents can be added to this This alloy, when used as the high expanding component in thermostatic bimetals, exhibits the same physical characteristics as the conventional nickel-chromium-iron alloy, but instead of being subject to phase transformations within the temperature range 196 C.-250 C., remains totally in the austenite phase. As a result, over this range,

3,625,603 Patented Dec. 7, 1971 ice the resulting bimetal is completely stable, its flexivity is unimpaired, and there is no discrete volume change. This permits my bimetal to be used in applications wherein the reduced flexivity of normal bimetals is objectionable, as for example, in bimetal thermometers.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS A specific alloy composition falling within the ranges recited above was formulated as follows:

Percent Nickel 21.31 Chromium 3.85

Manganese 1.59 Carbon 0.17

Silicon 0.14

Phosphorous O-0.025 Sulfur 0-0.025

Iron, balance.

A bimetal was fabricated using this specific alloy as high expansion component and Invar (nominal 36% nicke1, balance iron) as the low expansion component. No phase transformations could be observed over the temperature range of l96 C. to 250 C.; the fiexivity was unimpaired; and there was no discrete volume change.

Other typical compositions of my alloy are set forth in the tabulation below.

Ni Cr Mn Si (3 Melt number:

While I have described my invention with particular reference to the embodiments described above, my protection is to be limited only by the terms of the claims which follow.

What is claimed is:

1. A bimetal comprising:

a first metallic layer designated as a low expanding component, said first layer being composed of Invar;

Iron, balance.

2. A bimetal as set forth in claim 1 wherein the second layer contains 21.3% nickel, 3.85% chromium, 1.59% manganese and 0.17% carbon.

References Cited UNITED STATES PATENTS 1,953,229 4/1934 Heron 128 2,725,493 1l/1955 Mitchel 75-128 HYLAND BIZOT, Primary Examiner 

